[Rob Colatutto]

If your looking for a very simple 4 motor drive, probably one of the most simple I've seen that don't use gears would be from my high school teams (263) 2001 robot. Simply just the fp/bosch. (2001 was before the Atwood was added to the kit for anyone newer) fp(with its gearbox) geared up 1:3 to mate with the bosch(and its gearbox in low) and then geared 1:3 back down to a 12 inch wheel and ran about 5.5ft/s. Simple and elegant, 2001 LI regional winner and 2001 LI Delphi Driving Tomorrow's Technology winner. you could take that from the bosch and gear 1:1 to an 8 inch wheel and go approx 10ft/s if you are looking for a faster drive. A good approx of the robot speed can be done by taking
(wheel rpm X wheel diameter X pi) / 12 / 60
There are many old threads on this if you just look for them.
Another 4 motor drive example without gears is a timing belt combiner. (263 2002) The Atwood added in 2002 had a cluster gear given with it that mated with its output shaft. Then we attached a small 5:1 timing belt reduction onto that and it mated well with the bosch (and its gearbox in low). Then we did a sprocket reduction to the wheel. However both these designs required us to take appart the bosch gearbox and modify the output shaft to a standard 3/8 axel. Not a hard modification to do on your own.